Today, wind and the medieval mind. The University
of Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
created them.

What do you suppose a
medieval miller thought it was that caused the wind
to drive his mill? What invisible efficacy rode in
the air to grind his grain? The wind still captures
our imaginations, even when we know about
air, kinetic energy, and force balances. What must
it have meant when people knew none of that?

The ancient languages offer a remarkable answer.
All of them used the same word for wind, for
breath, and for soul. In Sanskrit that word is
atman; in Latin it's either spiritus
or anima; in Hebrew it's ru-ach; and
in Greek it's pneuma. You find pneuma
and spiritus in air-related words like
pneumatic and respiration.
Atman shows up again as the German verb
atmen which means to breath and
ru-ach is probably kin the the German word
rauch, for smoke. The Russian word for
spirit, duh, has many wind-related cognates.
Duhovyia intrumenti, for example, means
wind instruments.

The connection is that both the wind and the soul
were the breath of God. Genesis begins with God
breathing a soul into Adam, and medieval engineers
saw nothing less blowing their windmills. The power
source was mystical. Indeed, some historians
suggest that power-producing windmills evolved out
of ancient Buddhist prayer wheels, which were spun
by sail-like propellers. And, in that sense,
spiritus may have preceded power.

By the early nineteenth century, we understood the
wind in technical terms; but it'd lost none of its
metaphorical power. Listen to these words from
Percy Shelley's Ode to the West Wind:

Of course, Shelley's wind was more than just
spiritus. It was a renewing spirit, a
cleansing new broom. That's the same imagery we use
when we tell each other, "It's an ill wind that blows no good."

The world is girdled with prevailing winds.
Shelley's westerlies prevail in a band around the
45th parallel. That's why New York is two hours
farther from London by air than London is from New
York. Below the westerlies are trade winds. The
trade winds are bounded by two bands nearly devoid
of wind. Above are the "horse latitudes" (so called
because horses on ships becalmed in that region
were often killed to save water). On the equatorial
band below the trade winds are the doldrums,
a word that also means dis-spirited.

Today the wind again rises as a
power source. Stand in the midst of one of the
new windmill farms, and you can feel pneuma,
atman, and spiritus driving our dead
thoughts "like wither'd leaves, to quicken new birth."
Windmills won't be the final answer to our
energy needs. But they do remind us to see mystery
within reality, even as our medieval forebears did.
For no useful answer to any problem as ancient as
energy supply will ever arrive without bearing a
dimension of surprise, rebirth, and
spiritus.

I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.